When an erbium-laser pulse is directed into water through a small-diameter fiber tip (FT), the absorption of the laser energy superheats the water and its boiling induces a vapor bubble. We present ...the influence of different FT geometries and pulse parameters on the vapor-bubble dynamics. In our investigation, we use a free-running erbium: yttrium aluminum garnet (Er:YAG) (
) laser that was designed for laser dentistry. Its pulse is directed into the water through FTs with a flat and conical geometry. Our results show that in the case of the conical FT, a spherical bubble is induced, while a channel-like bubble develops for the flat FT. The ratio between the mechanical energy of the liquid medium and the pulse energy, which we call the optodynamic energy-conversion efficiency, is examined using shadow photography. The results indicate that this efficiency is significantly larger when a conical FT is used and it increases with increasing pulse energy and decreasing pulse duration. The spherical bubbles are compared with the Rayleigh model in order to present the influence of the pulse duration on the dynamics of the bubble's expansion.
The goal of this research is to use the information contained in the mechanisms occurring during the laser tattoo removal process. We simultaneously employed a laser-beam deflection probe (LBDP) to ...measure the shock wave and a camera to detect the plasma radiation, both originating from a high-intensity laser-pulse interaction with a tattoo. The experiments were performed
(skin phantoms),
(marking tattoos on pig skin), and
(professional and amateur decorative tattoos). The LBDP signal includes the information about the energy released during the interaction and indicates textural changes in the skin, which are specific for different skin and tattoo conditions. Using both sensors, we evaluated a measurement of threshold for skin damage and studied the effect of multiple pulses.
results show that a prepulse reduces the interaction strength and that a single strong pulse produces better removal results.
We present a novel method for real-time 3-D body-shape measurement during breathing based on the laser multiple-line triangulation principle. The laser projector illuminates the measured surface with ...a pattern of 33 equally inclined light planes. Simultaneously, the camera records the distorted light pattern from a different viewpoint. The acquired images are transferred to a personal computer, where the 3-D surface reconstruction, shape analysis, and display are performed in real time. The measured surface displacements are displayed with a color palette, which enables visual feedback to the patient while breathing is being taught. The measuring range is approximately
in width, height, and depth, respectively, and the accuracy of the calibrated apparatus is
. The system was evaluated by means of its capability to distinguish between different breathing patterns. The accuracy of the measured volumes of chest-wall deformation during breathing was verified using standard methods of volume measurements. The results show that the presented 3-D measuring system with visual feedback has great potential as a diagnostic and training assistance tool when monitoring and evaluating the breathing pattern, because it offers a simple and effective method of graphical communication with the patient.
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